Sunil Kumar

Indian Institute of Technology Delhi, India

“Ultrafast transient spin and orbital currents in metallic heterostructures”

Terahertz (THz) time-domain spectroscopy using efficient sources and detectors of THz radiation has become a powerful experimental tool for non-destructive testing of materials and can be used to probe various fundamental linear/nonlinear physical processes. In modern applications, compact and efficient THz sources and detectors are in demand which are cost-effective and can be applied in a broad frequency range. Femtosecond laser excited spintronic heterostructures have emerged as a potential candidate for powerful and broadband THz radiation sources. Increasingly popular systems in this regard are the bi- and tri-layer combinations of thin films of ferromagnetic (FM) metal and nonmagnetic (NM) heavy metal. Inverse spin Hall effect (ISHE) in the NM layer is majorly considered as the main mechanism to develop a transient current source which emits THz radiation. We have used THz emission spectroscopy to study the evolution of the THz emission from modified heterojunction in such heterostructures. In this talk, I will discuss some of the recent results from our laboratory [1-4].

[1] Sandeep Kumar and Sunil Kumar, Nature Communications 14, 8185 (2023).
[2] Sandeep Kumar and Sunil Kumar, Journal of Applied Physics 134, 170901 (2023).
[3] Sandeep Kumar and Sunil Kumar, iScience 25, 104718 (2022).
[4] Sandeep Kumar and Sunil Kumar, Applied Physics Letters 120, 202403 (2022).

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